


Rise of the Fallen

by Nymphfantasy



Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell, Apocalypse, Eventual Smut, F/F, F/M, Hurt/Comfort, Minor Character Death, Multiple kinks, Other Additional Tags to Be Added, Slow Burn
Language: English
Status: In-Progress
Published: 2018-01-12
Updated: 2018-01-12
Packaged: 2019-03-03 18:55:08
Rating: Mature
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 2,773
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13347405
Author URL: https://archiveofourown.org/users/Nymphfantasy/pseuds/Nymphfantasy
Summary: You were having such a great night, binge-watching your show, eating popcorn. Then you get a call from your best friend and that is the beginning of the end of the world as you know it. Monsters are real, they are free, and your world will never be the same again.





	Rise of the Fallen

**Author's Note:**

> Hey! Thanks for clicking on this fic. I hope you like it and please leave a comment because it would really make me happy.
> 
> Also, extra special super thanks to my amazing Beta, Dizplicity! Please go check out her tumblr because she is super cute and it has a link to her awesome art blog. I don't know how I got such a talented friend, but I'm really lucky to have her in my life. ----------> http://dizplicity.tumblr.com/
> 
> Disclaimers: I do not own nor did I have any hand in creating Undertale. It is all the amazing work of Toby Fox. This is merely a fan made story based on his original work. I make no profit from this work and I do not plan to.  
> I also did not come up with the idea for the Underfell AU. This story just has some of my own headcanons, plus a few universal ones throughout the Underfell community.  
> Finally, prepare for a bunch of parody names of popular stuff in pop culture because I didn't want to have to put 16,000 disclaimers in here.
> 
> Enjoy!

Sitting on the couch, wrapped in one of your softest blankets with a bowl of popcorn in your lap. You are binge-watching season 2 of Peculiar Items on Flicknix and are currently on the edge of your seat because everyone you care about is surrounded by monsters. You’re so focused on the television screen that when your cell phone starts obnoxiously ringing and buzzing from its place on the coffee table, you nearly jump out of your skin, causing your popcorn to spill everywhere. However, you quickly realize that the unexpected noise is just your damn phone, and you silently curse whoever it is that decided to call you at this exact moment. Reaching out for your laptop, you pause the show to pick up your phone, swiping the green icon up to answer without even looking. 

“Hel-” Before you can even finish your first word your friend Emily starts excitedly rambling into your ear, her voice breathless and a little louder than necessary.

“Y/N!! You need to get in your car and come into town immediately! You won’t believe what’s going on! I don’t even think I believe what’s going on! If I wasn’t seeing them in person with my own eyes, I definitely wouldn’t believe it! Seriously, they are so big and- Those teeth! It’s fucking terrifying but the kid that’s with them is super cute and they are using this megaphone to like, talk to everyone and- HOLY SHIT! Is that a talking flower?!” You are completely overwhelmed by Emily because of how fast she is talking and really you are having a lot of trouble trying to process everything. Finally, you give up trying to understand and just yell into your phone. 

“EMILY!!”

“-yeah?”

“I have no idea what you are trying to say. Slow down and try again.” You hear a small groan on the other line and you can’t help thinking that this could have been avoided if she had just calmly talked to you from the beginning.

“Dude, there’s no time! Just hurry up, get in your car, and get your ass over to my place immediately. I’ll meet you there and explain on the way.” Now it’s your turn to groan as you look at the paused TV screen in front of you, but you are already setting what remains of your spilled popcorn aside and are untangling yourself from your blanket.

“Alright, I’ll be there in 10.”

“Make it 5!” She says with finality before hanging up on you.

Groaning again, you slip your phone into the back pocket of your jeans and head over to your front door. Once there, you slip on your sneakers, which you kicked off haphazardly when you first walked in, and pull your jacket off the coatrack that sits beside the door. Putting your jacket on, you reach into the pocket and pull out your car keys, happy that for once you actually remembered where you had left them. Walking out the door, you don’t bother to lock it because you know your parents will be home in the next hour or so and the fact that you live in such a small secluded area makes the chances of being robbed pretty slim. You reach the driver side door of your car and slide in smoothly, your hand already moving to put the key into the ignition. With a quick turn of your wrist, your car comes to life. Reaching back, you pull your seatbelt across your body, click it into place, and the next thing you know you’re pulling out of your driveway and speeding down the rough backroad that your house is located on. 

As Emily ordered, you waste no time getting to her house, but you have to admit you may have broken a few traffic laws to get there within the allotted five minutes that she gave you. Emily is already standing in her driveway waiting for you when you pull up and park. Looking at her through your front windshield, you can already see she is bursting with energy and an array of emotions is playing out on her face. You quickly unbuckle and hop out of your car. Before you can even finish shutting the door behind you, she is already by your side.

“WHAT TOOK YOU SO LONG?!” She exclaims with exasperation as she grabs your hand and starts to drag you away from her house and down the street towards the town. You were curious to why you were walking into town instead of driving, but since you could easily walk from one end of your small mountain town to the other in about 30 minutes you weren’t too surprised by her actions. 

“What do you mean?! This is probably the fastest I’ve ever gotten to your house from mine.” You complain knowing that regularly the drive to Emily’s house, located on the very edge of town, usually takes you at least ten minutes tops. “I broke so many traffic laws that if our police department was actually worth a damn I’d be in jail right now.” Emily doesn’t seem to hear you though as she keeps walking and immediately changes the subject.

“You aren’t going to believe this, but trust me they’re real!” She says a bit cryptically and you can’t help being a bit annoyed because you would really like to know why the hell you had to come over so quickly and why she is acting so weird.

“Emily, would you just explain what is going on?” Your voice comes out a bit exasperated and you are having trouble not shooting daggers at her head for tearing you away from your show. Though as you’re walking, you start to notice that you and Emily aren’t the only ones headed further into town. With a quick glance around, you see the familiar faces of neighbors, old classmates, parents of your classmates, and basically every other townie. Everyone seems to have varying expressions of disbelief, fear, curiosity, and excitement as they all head in the same direction. 

“Monsters, Y/N, monsters….” You have never heard your friend sound so serious in your life, and to make things even more uncanny she even stops walking and looks you dead in the eye before she speaks. 

“Monsters? What do you mean monsters?” You now have more questions than when you started and you suddenly have a feeling of great unease as she continues to lead you forward. 

“Like, real monsters. You’ll understand once you see them yourself.” She says with confidence and continues walking on. 

For the next few minutes you both walk in silence as you try and comprehend what is going on. Monsters, seriously? Does she mean like the kind in fairytales and kids movies, or like the kind in scary stories and horror films, where the dumb high school kids get eaten alive in the first ten minutes? Your thoughts get interrupted when you notice that you aren’t actually heading towards the center of town like you thought, but are instead going past it, towards the base of the mountain. To your knowledge, the only things over that way are a few hiking trails and the old collapsed cave entrance, which everyone thought used to be an old coal mine. You look at your friend with confusion, but don’t bother asking where exactly you are heading because you figure you’ll find out soon enough anyway. 

As you get closer to the mountain, the more people there are. It seems like the entire town is here, well except for your parents, since they are two towns over having their weekly date night. Making your way forward, you and Emily have to start weaving past the crowd, and you can hear the metallic sound of someone speaking through a megaphone up ahead, but you can’t quite make out what they are saying over the growing rumble of voices from all around. You’re now walking down the worn dirt road that leads to the old cave entrance and have to be careful about where you place your feet because fallen limbs and rocks cover it. Even though you’re trying to be careful, you still strain your neck to see over the heads of the people, trees, and other foliage around you. Finally, the path starts to widen as you get closer and the crowd in front of you stops moving. 

That’s when you finally start to notice the dark shapes the seem to loom over the people farthest in front of you. The light of the setting sun is casting everything in shadows and the dim light is making it pretty hard to make out what the shapes are. Even though you can’t make out exactly what the shapes are, you can see that they are definitely moving and that they must be very large for them to stand so high over everyone. Soon you start to notice that you can now hear the metallic megaphone voice more clearly since you are closer. You were so distracted by the foreign shapes that you hadn’t noticed at first, but now you focus on what is being said even though you still can’t see the speaker.

“Everyone, please don’t be afraid! These monsters are my friends and they don’t want to hurt anyone. They just want to live amongst humans on the surface freely. They have been trapped for far too long underground that they can’t even remember what it’s like to live with the sun shining down onto their heads, or to look up at night and see the stars and moon sparkling in the vast reaches of the sky. Things that we all seem to take for granted, the monsters have been forced to live without. Please see not with your eyes, but with your heart and soul! See that they are not just monsters, see that they are people too, with thoughts and feelings and dreams of their own!” You quickly find yourself being carried away by the passionate speech you are hearing. You now realize that those looming shapes have to be the monsters and this voice has to be that of the child you vaguely remember Emily talking about on the phone earlier. 

“Dammit! We need to get closer so that we can actually see. This is what I get for going all the way home to get you.” Emily complains from beside you. You shrug your shoulders at her statement, not really feeling bad about her losing her spot earlier because of you. 

Suddenly, she takes hold of your hand and starts to shove her way through the crowd. The people around you glare or complain, but she ignores them all, the look on her face full of determination as she drags you forward. You, in turn, just give short apologies and do your best to not accidentally hurt anyone. You’re so focused on trying not to fall over someone else and giving apologies, that you don’t even notice that you have somehow made it to the front, and you stumble forward as you break free of the last line of people. Turning your head to face forward, you catch a quick glance of the monsters before falling flat on your face.

Even though you just fell down, you barely register any pain or the fall at all because of how stunned you are by just a simple glance of the monsters. Quickly, you push yourself up off the ground and whip your head up, coming face to face with a small brown-haired child in a red and black striped sweater. They look completely taken by surprise as they look at your now dirt covered face, a small cut on your cheek starting to bleed. You are less surprised to see them though and are more surprised by the giant yellow flower that sits coiled around the kid’s shoulder. The flower has a face and is staring right at you. All you can do is stare back. 

“Holy shit….” You finally manage to speak and those are the first words that leave your mouth. 

The child and the flower seemed unfazed by your language, but someone beside them starts to break into a gruff laughter. Your head jerks to the side, you were so focused on the flower that you completely forgot about the other monsters that you had only caught a glimpse of before. The one laughing at you stands about a foot or two taller than the kid and is wearing black shorts, a red turtleneck sweater, and a black coat with a fur-lined hood. 

Oh, and he is also a skeleton. 

He is unlike any skeleton you have seen before. You’d say he is almost cartoonish looking, if the sharp fangs that make up his mouth weren’t so horror movie like. Your jaw actually drops once you take him all in. This seems to amuse the skeleton further as he starts to laugh even harder and bends over, clutching at his midsection. Suddenly, a clawed hand covered in a red glove comes down and smacks against the back of his skull and immediately shuts him up. A small hiss escapes his strangely malleable mouth, as he clutches his round white head. 

“Sans would you please shut up?! How I got stuck with such a useless failure of a brother I will never know!” The owner of said hand is yet another, albeit much taller, skeleton.  
Dressed in finely polished back armor, tight hip hugger jeans, and with a bright red scarf tied around his neck, this skeleton looks extremely imposing, and you can feel a shiver of fear run across your spine. He seems to glare down at you, though it is a little hard to tell since he doesn’t actually have any eyes, just two impossibly black sockets. Suddenly, he is leaning down towards you, his gloved hand reaching out for you, and you shrink back, fear causing your stomach to clench as you panic slightly, worried about what this terrifying creature is going to do to you. Your reaction causes him to pause for a moment and you notice that his fang like mouth actually seems to curve up into what you can only describe as a smirk. In the back of your mind you wonder how a skull can smirk, but that thought is quickly squashed as the skeleton grabs your arm and not so gently lifts you up off the ground. 

“HUMAN! I know I, The GREAT PAPYRUS, am very imposing and that you obviously can’t help but want to kneel at my feet and worship me, but now is not the time! Frisk is trying to give a speech and if you know what’s good for you, you will stand quietly and listen!” The skeleton speaks to you in a commanding voice and you obediently nod your head, only sparing a small glance at the kid when he gestures toward them. You don’t dare try and say anything. You are still very afraid, and it must show on your face because the skeleton just smirks again before turning to look at the kid himself. 

Finally, you tear your gaze away from him and look across at all the monsters that are now crowded around in front of you. They are all different shapes and sizes, but a majority are very large and it seems that most of them have very sharp looking fangs and claws. They are also all wearing red and black which you think is kind of weird, but you don’t really have much time to think about it because the kid, Frisk, was clearing their throat and speaking into the megaphone again. 

Frisk then proceeds to talk about how they had fallen into the underground and traveled through it, befriending every monster they met along the way. They retold how, with the help of their new monster friends, they broke the barrier that had been created by human wizards and freed everyone. You find yourself enraptured by their tale and want to ask them for more details, but you are still too frightened of the monsters to even try and speak up. 

As Frisk talks, you find it harder and harder to look away from the monsters and now you are openly staring at them, your eyes traveling over them, taking in every detail. Monsters are real. There is no doubt about it now. They are real and they are free and your world has now changed forever, though you have yet to realize how much more it is going to change from here onwards.

**Author's Note:**

> Whew! This first chapter actually changed a lot from what I originally had planned because my first plan was basically crap. Anyway, I'd really appreciate any thoughts you might have on my fic and I welcome any constructive criticism. This is my first fic in a long while so I'm kind of rusty, but I really hope you like it so far. For those of you that aren't into smut don't worry it won't be for awhile longer, though I may through in a sexy scene here or there in the meantime.
> 
> I want everyone to know now that I will be working 60 hour weeks soon so the next chapter probably won't be out for awhile, but I plan to make it longer than this (for now anyway). For now, I am open to any suggestions you might have and if there is something specific you want to see happen let me know. I made this to be pretty much self-indulgent, but I love to indulge others as well. Also, I'm trying to decide whether I should throw in some UF!Sans/Reader as well or just keep this strictly UF!Papyrus/Reader, so let me know what you would prefer.
> 
> Finally, I just want to thank you again for reading and I hope that you stick with me, even with my slow updates because I really want to make this a great fic.


End file.
